Plouffe served as campaign manager for President Obama's 2008 campaign. Following Mr. Obama's election, Plouffe became senior advisor to the president in 2011, replacing David Axelrod, a position he held until 2013.

Uber, a five-year old San Francisco-based start-up that connects users to drivers through a mobile app downloaded to smart phones, has expanded rapidly around the world in recent years. It currently operates in more than 100 cities in 43 different countries. A recent round of financing valued the privately-held company at $18.2 billion.

Yet this expansion has angered its competitors, notably the taxi industry, which has not been shy about voicing its opposition to the upstart whose disruptive tactics endanger their livelihoods, they say.

Last week, Uber said it would disobey a Berlin ruling banning the company from operating in the city. Despite threats of fines as high as $33,000, Uber said it would appeal that decision, which followed a ban in Hamburg that was subsequently suspended after Uber challenged the decision. And in June, more than 30,000 cab and limo drivers clogged traffic in European capitals to protest Uber, which has been accused of operating without proper licensing and registration – which are expensive to obtain – and of jeopardizing passenger safety.

These tensions in Uber's face-off with the taxi industry were evident in the language used in statements by Mr. Kalanic and Plouffe. For example, they both referred to the taxi industry as a "cartel," emphasizing Uber's position as an outsider trying to take on a fiercely held monopoly.

"Uber has the chance to be a once in a decade if not a once in a generation company," Plouffe says in a statement. "Of course, that poses a threat to some, and I've watched as the taxi industry cartel has tried to stand in the way of technology and big change. Ultimately, that approach is unwinnable."

Uber has also recently been locked in a war of words with competitor Lyft. Both companies have accused the other of hostile business practices that include ordering rides from the other's service and then abruptly canceling, in theory to mar the competition's reputation for reliability and to waste competing drivers' time and money.